A detailed statement of work was prepared to describe the activities to be carried out by the AFRIMS group in Bangkok, Thailand. An Interagency Agreement (A-AI-12-051-0000-0000) was executed between NIAID and the U.S. Army Medical Research and Materiel Command and will become effective on 09-01-2012. This agreement will govern the activities between LID and AFRIMS and was funded by CAPS, LID and Division of Clinical research. CAP funding will be used to support this clinical trial, including the required serological assays, viremia assays, and other clinical activities associated with the evaluation of the tetravalent dengue vaccine. The purpose of this project is to evaluate a live attenuated tetravalent DENV vaccine candidate with regard to safety, tolerability, genetic stability, and immunogenicity in humans, and to study the host's immune response to these viruses. Six months after primary vaccination, participants will receive a second dose of tetravalent vaccine and will be followed for an additional 6 months. The study will enroll 266 subjects in a double-blind, placebo-controlled clinical trial.